Muffler / Exhaust Update 2
I've been working on my exhaust. In order to meet my "production car" type of interior sound level (>70dB) I know I have to tackle the primary noise producer. We will spend hundreds of dollars on items in an attempt to make the interior quiet (Or, for the reality of the GTM....Manageable) to only find out that it's still very loud and you have to let off the "go pedal" in order to have a conversation or hear something besides the exhaust note.
What follows is how I am addressing the exhaust in my attempt to quiet the primary noise maker. While I had the exhaust off I decided to add a Wide-band O2 sensor bung for future use. For the LS the wide-band needs to be on the LH exhaust side and pre-cat for best sensor accuracy. I drilled a .75" hole and tapped the two higher curves flat with a hammer to give the bung a ~flat surface since it was not the flanged style. I welded it on and checked the weld for leaks. I'm progressively getting better with the MIG.
I cleaned the pipes and used a 2000 degree flat black high heat rustoleum. I followed this with header wrap that I soaked in water over night. Once the wrap was dry I locked the wrap in with DEI black silicone.
I used .5" Armor Exhaust Heat Shield to wrap the cats. Heatshield Armor insulation features an inner ceramic liner that makes it capable of withstanding 1,800 degrees F continuous and 2,200 degrees F intermittent. This should keep more heat in the cats, away from the CV boots and outside of the engine bay.
More to follow....................................
What follows is how I am addressing the exhaust in my attempt to quiet the primary noise maker. While I had the exhaust off I decided to add a Wide-band O2 sensor bung for future use. For the LS the wide-band needs to be on the LH exhaust side and pre-cat for best sensor accuracy. I drilled a .75" hole and tapped the two higher curves flat with a hammer to give the bung a ~flat surface since it was not the flanged style. I welded it on and checked the weld for leaks. I'm progressively getting better with the MIG.
I cleaned the pipes and used a 2000 degree flat black high heat rustoleum. I followed this with header wrap that I soaked in water over night. Once the wrap was dry I locked the wrap in with DEI black silicone.
I used .5" Armor Exhaust Heat Shield to wrap the cats. Heatshield Armor insulation features an inner ceramic liner that makes it capable of withstanding 1,800 degrees F continuous and 2,200 degrees F intermittent. This should keep more heat in the cats, away from the CV boots and outside of the engine bay.
More to follow....................................
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Muffler (Magnaflow) Update
This evening I started the The car in order to listen to the exhaust. Thought it does sound deep /nice, I really do not like how loud it is. I am about 99% sure I will be pulling them.
Magnaflow Mufflers
Prior to this I had a set of Cherry Bomb turbo mufflers installed. I was very pleased with how the mufflers lowered the sound level of the exhaust. You can check out the videos below and the cart videos to get an idea. The trade-off was the loss the "H" portion of the H-pipe. Mike (MikesPMS) is using the H pipe with a set of dual tip Pacesetter Monza exhaust tips which are glass-packed resonators with slash-cut outlets. Though still a bit loud, His exhaust has the "exotic sound". Mike and I are both running a stock LS6 and after hearing his exhaust, with the tips, I decided I should find a way to connect both sides of the exhaust.
If you're familiar with the GTM, you know that Kooks makes a full exhaust system. I opted not to purchase the kooks system for a few reasons. It sounds great, but it is LOUD. Race mufflers and mid-engine equal an extremely loud cockpit. Its also ~$2000.00 shipped.
There was an exhaust thread recently on the Factory Five Forum. STLMARSHALL built an LS1 powered Daytona Coupe. He is running a set of MagnaFlow Performance mufflers #14363. After checking the specs on the muffler I decided to use them. The case of the Magnaflow muffler is only 11" which is a full 2" shorter than the body of the Cherry Bomb turbo muffler. This along with taking the inlets/outlets down to ~1" allowed this system to terminate only 1/4" further aft than the Cherry Bomb system.
To install the Magnaflow mufflers I first cut the inlet/outlets down to 1" from the weld (~1 1/4"). I them made a 3/4" relief at 3 and 9 o'clock on both muffler inlets. I then cut the H-pipe 1" aft of the "H" portion of the pipe. The muffler clamps were placed on and the H-pipe was slid into the muffler's inlets. I then removed 1' from the H portion of the H-pipe and slid on the band clamp. I removed the current system and bolted in the new H-pipe with the Magnaflow mufflers installed. With the muffler clamps tight I used a ratcheting tie-down strap to pull the two sides together until I had 19" between the muffler outlets. I then torqued the band clamp that I placed over the H portion of the H-pipe to lock everything in place.
I still need to do a support bracket. I plan to use a set of muffler case straps (or my backup plan is to use some 11 gauge steel to fab a bracket using the bolts of the H section's band clamp) and tying the exhaust into the transaxle so that the the exhaust remains one with the drive train.
The Magnaflow Performance Muffler's straight through design is definitely louder than the Cherry Bomb chambered turbo mufflers. However the sound is very nice. I plan to do a sound clip soon that can be used to compare them.
If you're familiar with the GTM, you know that Kooks makes a full exhaust system. I opted not to purchase the kooks system for a few reasons. It sounds great, but it is LOUD. Race mufflers and mid-engine equal an extremely loud cockpit. Its also ~$2000.00 shipped.
There was an exhaust thread recently on the Factory Five Forum. STLMARSHALL built an LS1 powered Daytona Coupe. He is running a set of MagnaFlow Performance mufflers #14363. After checking the specs on the muffler I decided to use them. The case of the Magnaflow muffler is only 11" which is a full 2" shorter than the body of the Cherry Bomb turbo muffler. This along with taking the inlets/outlets down to ~1" allowed this system to terminate only 1/4" further aft than the Cherry Bomb system.
To install the Magnaflow mufflers I first cut the inlet/outlets down to 1" from the weld (~1 1/4"). I them made a 3/4" relief at 3 and 9 o'clock on both muffler inlets. I then cut the H-pipe 1" aft of the "H" portion of the pipe. The muffler clamps were placed on and the H-pipe was slid into the muffler's inlets. I then removed 1' from the H portion of the H-pipe and slid on the band clamp. I removed the current system and bolted in the new H-pipe with the Magnaflow mufflers installed. With the muffler clamps tight I used a ratcheting tie-down strap to pull the two sides together until I had 19" between the muffler outlets. I then torqued the band clamp that I placed over the H portion of the H-pipe to lock everything in place.
I still need to do a support bracket. I plan to use a set of muffler case straps (or my backup plan is to use some 11 gauge steel to fab a bracket using the bolts of the H section's band clamp) and tying the exhaust into the transaxle so that the the exhaust remains one with the drive train.
The Magnaflow Performance Muffler's straight through design is definitely louder than the Cherry Bomb chambered turbo mufflers. However the sound is very nice. I plan to do a sound clip soon that can be used to compare them.
C-5 Corvette 1-3/4” BBK Exhaust Header System
The BBK Ceramic Coated Short Headers arrived this evening. I ordered them on Sunday night after getting some info from GTMSomeday from the forum and reading the reviews. I'm looking to unleash an additional 15 or so RWHP and get a deep exotic sound that is still on the low end of the db scale with these working in combination with my turbo mufflers. They look good, but really will not be seen after my carbon fiber engine cover is installed.
I installed the headers. My engine and body with Hatch are installed on the GTM. I was able to access everything from the open hatch or from inside the GTM. I had to pull the plug wires, unplug the header O2 sensors, Unlplug the coolant temp sensor, unbolt the EGR Connections on both sides and unbolt the Cat pipes to get the stock headers out. Both had to removed from above. The driver's side BBK header dropped right in. However I quickly discovered that I need to unbolt the row of coils on the passenger side to get the BBK head in. Everything fit perfect. the only issue was that the forward most header pipe on the passenger side was touching or almost touching the top corner of the AC compressor manifold ( there may have been a mm or less of space). In stead of grinding the corner of the manifold and disturbing the integrity of the manifold and the compressor connection, I opted to make an indention in the header pipe. Other builders have had to cut out a section an weld in a fill piece on kooks headers in this location with GTMs with compressor manifold clearance issues. So I felt a small indention would be best. I simply marked, protected the ceramic finish and persuaded it with a few hammer taps. In the center of the indention I added 3/16" of depth. After bolting everything back up I fired up the engine
I installed the headers. My engine and body with Hatch are installed on the GTM. I was able to access everything from the open hatch or from inside the GTM. I had to pull the plug wires, unplug the header O2 sensors, Unlplug the coolant temp sensor, unbolt the EGR Connections on both sides and unbolt the Cat pipes to get the stock headers out. Both had to removed from above. The driver's side BBK header dropped right in. However I quickly discovered that I need to unbolt the row of coils on the passenger side to get the BBK head in. Everything fit perfect. the only issue was that the forward most header pipe on the passenger side was touching or almost touching the top corner of the AC compressor manifold ( there may have been a mm or less of space). In stead of grinding the corner of the manifold and disturbing the integrity of the manifold and the compressor connection, I opted to make an indention in the header pipe. Other builders have had to cut out a section an weld in a fill piece on kooks headers in this location with GTMs with compressor manifold clearance issues. So I felt a small indention would be best. I simply marked, protected the ceramic finish and persuaded it with a few hammer taps. In the center of the indention I added 3/16" of depth. After bolting everything back up I fired up the engine
The following info is from the BBK web site.
ALL BBK short unequal length 1997-2004 Corvette C5 headers are designed for direct bolt-on performance to the existing stock exhaust system. Each BBK exhaust header system are CAD designed and are manufactured with 1 3/4" CNC mandrel bent tubing for un-restrictive airflow and a one piece laser cut flange 3/8" for added strength and durability. ALL BBK exhaust headers are pressure tested to ensure leak free performance.
Each shorty unequal length exhaust header for the BBK 1997-2004 C5 Corvette has been designed and dyno tested at the BBK headquarters in Southern California to Maximize performance. After dyno testing our design for the Corvette C5 exhaust headers they have proven to give you an additional 10-13 rear wheel horsepower. BBK’s Corvette headers offer distinctive quality that guarantees many years of top performance.
These BBK CNC Series headers for the 97-04 Corvette are ONLY available with high-temp show quality Silver polished ceramic coating.
Each exhaust header kit comes complete with gaskets, hardware, and installation instructions.
ALL BBK short unequal length 1997-2004 Corvette C5 headers are designed for direct bolt-on performance to the existing stock exhaust system. Each BBK exhaust header system are CAD designed and are manufactured with 1 3/4" CNC mandrel bent tubing for un-restrictive airflow and a one piece laser cut flange 3/8" for added strength and durability. ALL BBK exhaust headers are pressure tested to ensure leak free performance.
Each shorty unequal length exhaust header for the BBK 1997-2004 C5 Corvette has been designed and dyno tested at the BBK headquarters in Southern California to Maximize performance. After dyno testing our design for the Corvette C5 exhaust headers they have proven to give you an additional 10-13 rear wheel horsepower. BBK’s Corvette headers offer distinctive quality that guarantees many years of top performance.
These BBK CNC Series headers for the 97-04 Corvette are ONLY available with high-temp show quality Silver polished ceramic coating.
Each exhaust header kit comes complete with gaskets, hardware, and installation instructions.
Video for Audio Comparison-Stock Headers, Cats and Turbo Mufflers |
Video for Audio Comparison-BBK Short Headers Installed, Cats and Turbo Mufflers. |
I placed the Camera in the same place and position for both clips. The sounds are not very different. I found the best way to compare them was to open both in separate windows and using headphones listen in small periods constantly switching between the two.
I noticed that the deep bellow is louder and more noticeable. I believe this is the tone that under acceleration becomes the tone we refer to as (that exotic car sound). These were both taken with the vehicle stationary. At some point in the near future I'll record a neighborhood drive with recording both the spectators view and from inside the GTM. Then I can compare them to the karting recordings.
I noticed that the deep bellow is louder and more noticeable. I believe this is the tone that under acceleration becomes the tone we refer to as (that exotic car sound). These were both taken with the vehicle stationary. At some point in the near future I'll record a neighborhood drive with recording both the spectators view and from inside the GTM. Then I can compare them to the karting recordings.